Various types of abrasive articles are known in the art. For example, coated abrasive articles generally have abrasive particles adhered to a backing by a resinous binder material. Examples include sandpaper and structured abrasives having precisely shaped abrasive composites adhered to a backing. The abrasive composites generally include abrasive particles and a resinous binder.
Bonded abrasive particles include abrasive particles retained in a first binder that can be resinous or vitreous. Examples include, grindstones, cutoff wheels, off-angle grinding wheels, hones, and whetstones.
Precise placement and orientation of abrasive particles in abrasive articles such as, for example, coated abrasive articles and bonded abrasive articles has been a source of continuous interest for many years.
For example, coated abrasive articles have been made using techniques such as electrostatic coating of abrasive particles have been used to align crushed abrasive particles with the longitudinal axes perpendicular to the backing. Likewise, shaped abrasive particles have been aligned by mechanical methods as disclosed in U.S. Pat. Appl. Publ. No. 2013/0344786 A1 (Keipert).
Precise placement and orientation of abrasive particles in bonded abrasive articles has been described in the patent literature. For example, U.S. Pat. No. 1,930,788 (Buckner) describes the use of magnetic flux to orient abrasive grain having a thin coating of iron dust in bonded abrasive articles. Likewise, British (GB) Pat. No. 396,231 (Buckner) describes the use of a magnetic field to orient abrasive grain having a thin coating of iron or steel dust to orient the abrasive grain in bonded abrasive articles. Using this technique, abrasive particles were radially oriented in bonded wheels.
U.S. Pat. Appl. Publ. No. 2008/0289262 A1 (Gao) discloses equipment for making abrasive particles in even distribution, array pattern, and preferred orientation. Using electric current to form a magnetic field causing acicular soft magnetic metallic sticks to absorb or release abrasive particles plated with soft magnetic materials.